Loading-coils for phantom circuits on aerial lines.



H. B. M.-PLEUEL & Ar H. OLSSON. LOADING COILS run Pn Ammwgcmcuus 0N AERIAL LINES.

APPLICATiUN FILED APR.27| 1914.

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Aug. 2 SHEETS- H. B. M. PLEUEL & A. H. OLSSON.

LOADING cons FOR PHANTOM cmcuns ow AERIAL LINES. APPLICATION FILED APR. 27. 1914. 77 m Patented Aug. 29, 1916.

2 SHEETS-SHEET 2.

, tallic casing. The stray tit HENNING BE 1':

LOADING-COILS F0151, PHANTOM CIRCUITS 0N AERIAL LINES.

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Specification of Letters Patent.

Patented Aug. as, rare.

Application filed April 27, 1914. Serial No. 834,665.

To all whom it may concern Be it known that we, HENNING' BERN- HARD MATHIAS PLEIJEL, a subject of the King of Sweden, residing at Stockholm, in the Kingdom of Sweden, and Axnr. HERMAN OLssoN, a subject of the King of Sweden,

residing at Stockholm, in the Kingdom of Sweden, haveinvented new and useful Improvements in Loading-Coils for Phantom Circuits on Aerial Lines, of which the following is a specification.

Overhead telephone lines were originally pupinized 'with single coils, that is to say, each branch conductor was provided with a separate coil at each point of loading. It soon became evident, however, that it is extremely difiicult, if not impossible in practice, to construct these single coils in such a manner that they will retain the same electrical properties continuously. As, how ever, this is absolutely necessary in order to avoid troublesome cross-talk, the practice has been adopted of employing-double coils for. overhead lines, and by this means, the requirements mentioned are sufficiently well fulfilled: If, however, such lines provided with double coils are duplicated, various difficulties arise. These difliculties and the means hitherto employed for overcoming them have been discussed at length in the specification which accompanied our application, Serial No. 834,664, wherein the object aimed at is to remove the stray field of the coils when the double lines are traversed by the currents of the duplex connection.

Tn overhead lines, the double coils of different pairs of lines are relatively far apart, and are each inclosed, according to the only method hitherto known, in a separate mefield is in this case harmful and to be avoided, because it induces eddy. currents in thisv metallic casing with the efi'ect of considerably increasing the specific damping of the duplex line.

The disadvantages inherent to the meanshitherto employed-such as increase of resistance due to the extra sets of coils and incomplete independence Where the lines are connected together by duplex coils-ere avoided according to the present invention seeing that not the stray field itself, but the harmful eflects of the stray field-due to the method hitherto employed of mounting the double coilsnamely, the. eddy currents, are removed. This enables the loading of the duplex line to be effected by the stray field instead of by extra sets of coils, so that the stray field need no longer be avoided.

By ractical experiment we have found that where coils of suitable size are used, a stray field of such force is created as to produce the self-induction necessary for loading the duplex lines. Double lines which are already loaded by coils in this manner may therefore be duplicated, should the necessity arise, without any further apparatus such, for instance, as extra coils, entailing expense or other disadvantages. That this stray field no longer gives rise to any eddy-current losses is a result which we obtain by forming the casings inclosing the coilshitherto composed of metal preferably cast ironof a non metallic and suitably non-hygroscopic substance such as glass, porcelain, or other composition possesslng similar properties. Moreover, other parts arranged adjacent to the coils are, as far as practicable, formed from similar material. 1

In the accompanying drawings, Figure 1 is a diagrammatic view illustrating the connection for multiple telephoning with coils mounted as described. A B is the one main line and A B the other. C and D are the telephones in the duplex line of which the two branches of A B are used in parallel as the one line and the two branches A B in parallel as the other. Fig. 2 is a vertical cross section taken on the line A-B in Fig. 3, of a coil-with its cover and suspension device and the connections for the lines, while Fig. 3 is a corresponding plan with the said cover removed. i

As shown in Fig. 1, the coils 1 are connected up in the same way as in single telephones. The coil 1, (see Fig. 2), with the iron core 2, is firmly held, by means of the screws 3, between the two insulating plates 4 and 5, whereof the late 5 is fastened at its projecting parts 6 see Fig. 3), by means of the disks 7 and the nuts 8 arranged on the screws 3, to the projections 10 in the porcelain cover 9. Between these projections 10, hollows are provided which corre spend with the projections 6 of the plate 5 in order. to allow of the insertion f the plate 5 into the cover. In the plate 5, four sc ew 11.. are faste ed, Which serve not only as connections for the four ends of the coils, but also to fasten the porcelain bottom 13 to the cover by means of the nuts 12. The points of insertion of the screws 11 into the bottom 13 are preferably formed as ordinary insulators. Moreover, on the plate 5 is arranged an upright plate 14, likewise composed of insulating material, on which two lightning arresters 15 for greater discharges and two vacuum lightning arresters 16 for lesser discharges are mounted. After the plate 5, with the parts mounted upon it, has been inserted into the cover, and turned so that the projections 6 lie 'over the projections 10, there will be spaces between these projections. These spaces have to be filled with pieces of insulating material which fit therein, and after the bottom 13 has been fastened in the manner described, the space between this and the plate 5 may be filled in by introducing suitable insulating material by way of the hole 17.

The upper part of the cover 9 is preferably coated internally with varnish, or the like, and powdered cork, in order to avoid a deposit of water withimthe cover, which latter is attached by means of the connecting bracket 18, 19, to the pole, whereupon the four ends of the double line are connected to their contact screws 11.

We claim 1. In an overhead duplex line loaded according to the Pupin system, wherein the main lines are loaded by double coils, induction coils wherein stray fields are produced by the currents in the duplex connection, while the main lines are, by means of said stray fields, loaded as branches of the duplex line.

2. In an overhead duplex line loaded according to the Pupin system, wherein the main lines are loaded by double coils, induction coils inclosed in non-conducting and non-hygroscopic casings and wherein stray fields are produced by the currents of the duplex connection, while the main lines are, by means of the said stray fields, loaded as branches of the duplex line.

HENNING BERNHAED MATHIAS PLEIJEL. AXEL HERMAN OLSSON.

Witnesses DAVID STENQUIs'r, ARvIs HoLMGnnN. 

